Also, sometimes with some very weird nonmanifold meshes you can get a situation where Blender cannot figure out which way to point the normals so that they are simultaneously "outward" and "coherent." My recommendation is always to make sure you're fully manifold before laying a finger on normals issues.

My experience is that Blender sometimes gets the normals wrong even when the mesh is manifold - and I don't think Shapeways tells you about problems with the normals until the mesh has passed the manifold test.

Hi, I opened the STL file in MeshLab (where you can see easily the faces with inverted normals on the back legs), and used the "Re-orient all faces coherently" option on the "Normals..." submenu of the "Filters" menu, and this seems to have fixed the problem. This solution isn't guaranteed either, but it often succeeds where Blender has failed.